Incubators of this type are used for receiving infants as well as prematures and newborns to isolate them in a protected atmosphere. The incubator air should be adjustable within certain limits in terms of temperature, oxygen content and humidity, and it should be possible to maintain these quantities within these limits. In particular, especially stringent requirements are made for temperature stability and uniform distribution of temperature in the vicinity of the resting surface. This is true both when the incubator is closed and during necessary treatment procedures to be performed on the patient. During such treatment, the openings provided for this purpose, such as access openings or relatively large flaps, have to be opened. The heat supplied to the interior of the incubator then should not escape into the colder ambient to more than the minimum possible extent and, even in the closed state, heat loss due to convection or radiant heat should be as low as possible.
Published German patent application DE-OS No. 31 00 932, discloses an incubator having a rectangularly shaped resting surface inside a hood, at the head and foot ends of which an air outlet and air inlet, respectively, are provided. Warmed air is blown from the air outlet into the hood interior via a recirculating apparatus and aspirated at the foot end via the air inlet. The circulating warm air is distributed in the bed region, where it should maintain a constant temperature. On the long side of the hood, there is a relatively large flap provided with manual access openings, which can be vertically opened and pivoted entirely out of the way. With the front flap opened, an additional air outlet for the warmed incubator air is made available, and this air outlet extends all the way along the long side of the resting surface. The warm incubator air now escapes at the head end as well as at the newly opened air outlet along the long side of the front flap, and is aspirated away via the remaining air inlet at the foot end.
In this known incubator, with the front flap opened, a warm-air curtain is to be provided which is intended to prevent an exchange of air with the ambient. This kind of air curtain, however, is only incompletely attained by means of the known warm-air guidance because warm air is now being blown out of two air outlet openings, the flow paths of which intersect in opposite directions, so that a closed circulation of air between the two air outlets and the single air inlet on the foot end can no longer take place. Instead, an aspiration of unwanted air takes place through the opened front flap, and a corresponding expulsion of warm air takes place out of the incubator interior. The result is an appreciable disruption of the temperature equilibrium in the incubator interior, and there is a considerable change in the temperature level in the vicinity of the resting surface.
Even with the front panel closed (and thus without the air curtain on the front side), the known air guidance does not produce the desired reduction of the heat loss of the infant from radiant heat. The outflowing warm air heats only the end faces of the incubator hood, which have a relatively small surface area, while in contrast, a considerable radiant heat loss continues to take place through the front and rear sides of the hood, which have a large surface area and are colder.
If the front side is closed and the manual access openings located therein are opened, then the front air outlet remains closed, and no warm-air curtain forms, so that cold air can enter from the ambient into the incubator interior.
Published European patent application No. 0 032 133 discloses an incubator having a cylindrically-shaped double-walled hood, which is divided into segments along the cylinder axis. With the hood closed, the warm air is blown via an air outlet at the rear side of the hood into the intermediate space of the double wall and then reaspirated out of the intermediate space at the front side. A plurality of openings in the inner shell of the double-walled hood allow a small portion of the warm air to enter into the interior of the hood. With the front side opened, the air circulation between the hood shells is interrupted, so that all the warm air is blown in via the openings in the inner shell into the interior of the hood. Since the air inlet along the front side is now completely opened with respect to the ambient, not only the warm incubator air but cold ambient air as well as aspirated, and a large proportion of the incubator air escapes into the cold ambient. Here again, a drop in the incubator temperature occurs which leads to considerable convection heat loss for the patient in the incubator. If the front side is opened completely, all the warmed incubator air escapes to the ambient, and maintenance of the previously adjusted air temperature is no longer assured.